Survey Techniques

Specializing in bat survey, especially in remote and challenging areas. There are vast regions around the globe that remain unsurveyed for bat biodiversity. Fundamental to conservation of biodiversity is knowing what species exist in an area!

Remote surveys are our specialty! Surveying bats often takes us where there are no roads. Cori has surveyed bats using canoe, whitewater raft, helicopter and pack mules.

In the photo at left, Cori and a colleague search for a bat’s roost using radio-telemetry.

Photo at right shows Cori stringing a net across a narrow canyon. The principle behind netting is to make sure you “wall off” a bat flyway as completely as possible.

When conducting bat surveys, Cori uses a combination of triple, double and single high mistnets on poles ranging from 8-24 feet in height. To maximize the chance of catching all species in an area, nets are set in cluttered and open conditions; dry-land and over standing water; edge habitats and flight corridors; potential night-roosts, etc. Custom and standard net lengths are used: 1.2, 1.6, 2.6, 4.5, 6, 9, 12, 15, 18 m and a combination of monofilament and standard thickness nets.

Harp Trap

There are two main methods of capturing bats: harp traps, shown here, and mistnets. While mistnets can be used in a variety of conditions, harp traps work best for narrow trails in thick forest , or at the mouth of caves and mines (as shown here).

Cori sets a mistnet in the photo at right. Part of her equipment repertoire is a large selection of mistnet poles. In this location, telescoping painter’s poles are ideal for holding up a net in marshy soil. Cori chooses from 5 different types of mistnet poles to best suit the survey conditions.

This long-eared bat is captured in a mist net. Using echolocation, bats are capable of detecting the fine mesh material. However, they may not always be paying close enough attention to their signals!

When a bat hits the net, it falls into a small pocket created by its weight. One has to be quick to get the bat out before it releases itself, as they will often chew a hole in the net!

After catching a bat in a mist net, it is placed into a clean cloth holding bag until it can be processed [photo left]. Calipers are used to measure the forearm [photo right, by AJ Fedoruk]. This length can be important in differentiating between some similar looking species.

Radiotracking bats at Dinosaur Provincial Park, Alberta. Foraging and roosting habitat can be determined using small radiotransmitters glued on the back of bats.

To learn about bat behaviour and ecology, transmitters as small as 0.27g can be glued between the scapulae of the bat. Depending on size of the transmitter and adhesiveness of the glue, bats can be tracked for several weeks. Through experimentation, it has been determined that transmitters need to be 5% or less of the bat’s body mass to ensure minimal interference with flight.

These pictures demonstrate the realities of bat research in the field—definitely not your average desk job! The photo at left shows Cori rapelling down a cliff face in search of a bat’s roost.

Doing research in the Gila Wilderness area of New Mexico meant going by pack horses.

The photo at right was taken as Cori and her teammates helicoptered in for the Nahanni survey in 2006.

The photo above shows that no channel of water is too deep to mistnet across when you have a bellyboat! Netting across narrow bodies of water is a great way to catch bats. Here in the Yukon where netting opportunities are limited, Cori couldn’t afford to be limited by chest waders, so nets were set across deep channels using flippers and a bellyboat.

At right, Cori and Michael measure and genetically sample bats. Michael completed a PhD and Postdoctoral Fellowship in grizzly bear ecology. As a husband and wife team, their company, Birchdale Ecological Ltd., specializes in ecological research of mammals [although they also research other animals such as snakes when mammals become too boring!].

The photo at right shows Dave Nagorsen of Mammalia Consulting, zip-lining a bat for acoustic sampling. Zip-lining involves tethering a bat [see close-up above] to a horizontally strung fishing line using a light bungee cord. As the bat flies back and forth on the “clothes line” created between the two small green poles, we record its echolocation calls.

Part of understanding the biology and distribution of a bat species involves being able to recognize the pattern of their echolocation call. Ultrasound calls produced by bats vary from individual to individual, from species to species, and between different types of geography.

With a light elastic cord tied loosely around the back of a bat’s head [they really don’t have much of a neck!], it can be kept near a recording unit while it flies, to ensure its acoustic signature is captured.